When erecting a fence, it is normal to erect a line of posts vertically in the ground and connect each post by fence panels, wooden rails, or wire such as barbed wire. When using fence posts it is especially essential that the posts are spaced to the exact width of fence panels and vertical.
One method of erecting posts is to dig a hole in the ground, temporarily hold a post in the hole in the vertical position and the correct distance from an adjacent post, and then pour concrete into the hole. A problem with this is that if the post does not stay vertical whilst the concrete is setting, or the post is not in the correct position, it is not possible to adjust the post position once the concrete has set. Also digging of a hole and mixing up the concrete is time consuming. Also at a later date it is hard to remove the concrete.
Another method of erecting posts is to use a “Metpost” or similar device which is a metal spike with a square section box at one end. The metal spike is hammered into the ground leaving the box just above ground, and a post is inserted and secured into the box. It is very difficult to hammer the spike into the ground so it is exactly vertical and in the correct position as it cannot be done with the post in the box, and stones or roots easily deflect the spike. Also it is difficult to create a rigid connection between the post and the box. It is also difficult to correct the position of the spike.